Hard-drive maker Seagate Technology has developed new digital-video recording technologies aimed at addressing concerns about capacity and digital-rights management.

Seagate representatives are demonstrating the new DVR features for cable service carriers at the National Cable Show conference in San Francisco this week.

For storage-hungry consumers, the company is showing an add-on 400GB external hard drive, which is being tested with cable operators. The drive at the show attaches to the Scientific Atlanta Explorer 8300 Series DVR. Seagate is also demonstrating a prototype 2.5-inch 120GB hard drive that can be added internally to set-top boxes.

On Monday, the company unveiled its DriveTrust software, designed to ease concerns about digital-rights management. DriveTrust allows cable operators and DVR makers to lock external storage products to a specific device, such as a set-top box. The software can be customized to work with a cable company's network.

DVR providers and cable companies represent a major opportunity for hard-drive makers. Cable giant Comcast recently began offering DVR service to its subscribers, and satellite companies DirecTV and Echostar have already used DVRs to attract new customers. Most digital services come with set-top boxes, and the addition of a hard-drive-based DVR to those boxes would open up an indirect market of millions of cable subscribers for hard-drive makers.

"We've done much of the R&D on these DVRs to make it easier for cable companies to roll out service to their subscribers," said John Paulsen, a Seagate spokesman. "The market has grown a lot in the last couple years, but the serious growth is yet to happen."

In the United States, 10.7 million DVRs are expected to ship by 2008, according to research firm IDC. As of 2004, about 4.4 million DVRs had been delivered.